Predetermined torque release wrench



R. G. wooDs 3,016,773

PREDETERMINED TORQUE RELEASE WRENCH 2 Sheets-Sheet 1 ilu @s Jan. 16,1962 Filed Deo. 12, 1958 mw f NEN/nl W We? G/f r r A E. E mM @j Jan. 16,1962 R. G. woons 3,016,773

PEEDETEEMINED TORQUE RELEASE WRENCH Filed Dec. 12, 1958 2 Sheets-Sheet 2e4 rraeA/ y:

Patented Jan. lb', 1952 dee 3,016,773 PREDETERMENED 'EQRQUE RELEASEWRENCH Robert Glen Woods, 3102 Grand Ave., Huntington Park, Calif. FiledDec. l2, 1953, Ser. No. 779,391 28 Claims. (Ci. 8l52.4)

The present invention relates generally to wrenches and moreparticularly to an improved adjustable torque wrench of simplied design.

A variety of torque wrenches have been heretofore marketed and devisedthat are assembled from ostensibly identical parts. Each of these partstheoretically must be held to extremely close tolerances, but due totheir geometry it is impractical to obtain these tolerances withconsistency. The resulting torque wrenches, while apparently beingcomposed of identical parts, are actually composed of parts which arenot identical. Accordingly, it is common practice in the manufacture ofsuch wrenches to provide integral means for Calibrating the wrench priorto the time it leaves the factory, in order to compensate for errors inmanufacturing tolerances. Once the wrenches have reached the iield, ifany breakage or deterioration of the parts occurs the wrench must bereturned to the factory in order to be recalibrated when new parts aresubstituted.

A major object of the present invention is to provide a torque wrenchcomprising a combination of parts of simple geometry each of whichreadily can be held to close tolerances in order to produce torquewrenches which do not require integral adjustment means to compensate orerrors in manufacture.

Another object of the present invention is to provide a torque wrenchhaving a geometry which enables the wrench to be repaired by the user inthe eld without changing the calibration of the wrench.

It is also an object of the present invention to provide a torque wrenchutilizing a cylindrical pivot or cam element adapted for breaking of thewrench within an extremely narror range of critical limits. When theload approaches the predetermined limit tor which the wrench is set, thewrench will break immediately upon the load on the wrench exceeding thepreset limit.

Another object of the present invention is to provide a torque wrench ofthis type in which any force applied to the handpiece in a directionother than the plane of the torque to be measured is absorbed by thewrench without affecting the present breaking point of the wrench.

It is also an object of the present invention to provide an adjustabletorque wrench with a simplied locking means to prevent variation from apredetermined torque limit for which the wrench has been adjusted.

An additional object of the present invention is to provide anadjustable torque wrench having a simple design and a ruggedconstruction whereby it will afford a long and useful service life.

These and other objects and advantages of the present invention will beapparent from the following description, when taken in conjunction withthe appended drawings wherein:

FIGURE l is a longitudinal vertical sectional view of an adjustabletorque wrench embodying the present invention;

FIGURE 2 is a reduced fragmentary sectional view of said wrench, withportions partly broken away in longitudinal section;

FIGURE 3 is a transverse sectional view, on an enlarged scale, takenalong line 3--3 of FIGURE l;

FIGURE 4 is a transverse sectional View, on an enlarged scale, takenalong the line 4-4 of FIGURE 1;

FIGURE 5 is a partial longitudinal Section of the Wrench in the area 5of FIGURE l and on an enlarged scale;

FIGURE 6 is a transverse sectional view taken on line 6 6 of FIGURE l;

FIGURE 7 is a transverse sectional view taken on line 7-7 of FIGURE 1;

FIGURE 8 is an elevational View partly in section and on an enlargedscale of an alternate form of cam or pivot element for utilization withsaid wrench;

FIGURE 9 is an elevational View, with parts broken away and in section,of an alternate form of lock means;

FIGURE l0 is a transverse sectional View taken on the line 10-10 ofFIGURE 9 showing details of the interior construction of the lock meansot FIGURE 9;

FIGURE ll is a view similar to FIGURE 9 and showing the alternate formof lock means in locking position; and

FIGURE l2 is a sectional view on an enlarged scale of the area 12 inFIGURE 11.

Referring to the drawings, a preferred form of adjustable torque wrenchembodying the present invention broadly comprises a head 2t having arigid downwardly projecting load-engaging member 2i and a pivotallymounted rearwardly projecting hinge member 22. The rearwardly projectinghinge member 22 is disposed within the forward end oi a tubular levermember 23 and, in turn, pivotally suports the lever member 23 formovement about an axis that is normally concentric with the axis ofrotation of the load member 21. At its rear end the lever member 23carries a threadedly adjustable hand hold 24- that is drivingly engagedwith a compression spring 25 enclosed within the lever member 23. Theforwardend of the spring 25 abuts a plunger 26 and a cam or pivot member27 is interposed between the forward end of the plunger 26 and the rearend of the hinge member 22. As will be apparent, rotation of the handhold 24 will vary the compressive force of the spring 2S. Variation ofthe latter in turn will vary the torque at which the camming element ormember 27 will break to permit relative angular movement to take placebetween the hinge member 22 and the lever member 23. When the operatorfeels such breakingj he is made aware that the torque applied by theload-engaging member 21 has reached the preset limit.

More particularly, the head Ztl is formed with an axially extendingpassage or counterbore 28 of oblate cylindrical conguration. The smalerend 28a of the counterbore is flattened at the poles of its minor axisand adapted to slidably receive the forward end of the hinge 22 as shownin FIGURE 1, and has a major axis greater than the diameter of theforward end of the hinge 22, as shown in FIG- URE 2. A vertical pin 29pivotally interconnects the hinge 22 and head 20 through the smaller end28a of the passage and has its axis coincident with the minor axis ofthe opening 28a. Since the pin 29 is offset but parallel to the axis ofthe load-engaging member 21, a slight lost-motion is permitted betweenthe head 26 and the hinge 22, the hinge 22 being s'ightly angularlymovable within the head 20. This relationship is indicated in FIGURE 2.

The larger rear end 28h of the passage 2S is flattened at the poles orits minor axis and adapted to slidably receive the outer diameter of thetubular cylindrical lever member 23. A pivot pin Sti interconnects thelever 23 and hinge 22 for relative angular movement about an axisnormally aligned with the axis of the load-engaging member 2l. Since themajor diameter of the passage 28 is substantially larger than the outerdiameter of the lever 23, an appreciative amount of limited relativeangular movement is possible between the head member 20 and the lever23, as is indicated in FIGURE 2. rIbis limit is irnposed by contact ofthe lever 23 with one side ofthe opening 28h at a point coincident withthe intersection of the major axis and thesurface defining the opening28h. This limit preferably occurs coincidentally with the engagement ofthe hinge 22 with the side Wall of lever 23.

In order to permit relative angular movement between the lever 23 andthe hinge 22, a ball and socket type of construction is utilized inthese parts around the pivot pin 3i?. Referring to FIGURE 5, it will beobserved that the hinge 22 is formed with a rearwardly facing convexshoulder 35i comprising a segment of a spherical surface having theradius R whose center is coincident with or lies on the longitudinalaxis 32 of the wrench as a whole. A complementary and concentric concaveball shoulder 33 is formed in the forward end of the lever 23. These twoshoulders permit free relative angular movement of the lever 23 andhinge 22 and within the range of such relative angular movement,portions of the interior diameter surface of lever 23 and hinge 22 areat all times in contact. The contacting surfaces of the hinge 22 andlever Z3 also provide a seal which will prevent the escape of lubricantfrom within the lever 23.

To limit relative angular movement of the lever 23 and hinge 22, thehinge is conically tapered to a reduced diameter. The rear end face ofthe hinge 22 is formed with a sloping-sided cavity 34. The width ofcavity 34 approximates the diameter of the cylindrical cam member 27. Arearwardly tapering truncated frusto-conical depression 35 is centrallyformed in the forward face of the plunger 26 with a bottom diameterequal to that of cam 27. The sloping walls of both depressions 34 and 35have an angle suiiicient to permit canting or shifting of the cam 27from side to side without contacting the walls of the depressions 34 and35. Thus, when the wrench breaks with the parts assuming the positionsshown in FIGURE 2, the cam 27 contacts each of the depressions 34 and 35in but a single point. It will be appreciated that upon the slightestshifting of the cam 27 out of coaxial alignment with the hinge 22 suchpoint to point contact occurs immediately so that an extremely sensitivebreaking point is achieved with this construction.

When the wrench is in the condition illustrated in FIG- URE 2, theneutral axis of the cam 27, in conjunction with the points of contact ofthe cam with the hinge 22 and plunger 26, will deiine a plane throughwhich force is transmitted between the hinge 22 and the plunger 26. Inorder for the point at which the wrench actually breaks to truly reflectthe torque limit for which the Wrench is set at that time it isdesirable that this plane be exactly coincident with the plane in whichtorque is actually being applied to the load. Accordingly, the passage28 in the head 2@ is formed with the aforementioned oblate conguration.When force is applied to the handhold 24 of the wrench having componentswhich resolve themselves into planes other than the plane in whichtorque is transmitted to the load, these other forces will tend to bedirectly absorbed by the head Ztl, hinge 22 and lever 23. In otherwords, for a given input force applied to the handle 24, an equalresultant force will not always be applied to the load member 21 withinthe plane of the app'ied torque. Some of the input force will bedissipated in planes other than the plane of the applied torque. Withthe arrangement just described, only the actual resultant forces appliedwithin the plane of the applied torque will have any effect in causingbreaking of the wrench. Thus, if the user of the wrench exerts a forceonly in a plane normal to the plane of the applied torque, such forcewill be directly absorbed by the direct connection between the head 20,hinge 22 and lever 23. Other forces which resolve themselves into planesbetween the plane of the applied torque and a plane normal to that ofthe applied torque will be reflected in the plane of the applied torqueonly in proportion to vector resultants within the plane of the appliedtorque.

In order to adjust the aforedescribed torque wrench to a desired torquelimit, the compressive force of the spring 4 25 can be varied byrotation in an appropriate direction of the handhold 2d. The tubularhandheld 24 is adapted for telescopic slidable movement on the lever 23with its rear end being closed by an end wall 36. A central opening 37is formed in the end wall 36. This opening 37 has a driving connectionwith a splined reduced-diameter rear end portion 38 of a cylindricaldrive member 39 which is coaxially disposed within the rear end of thelever 23. in order to compensate for variations in the spring rates ofostensibly identical springs 25, one or more adjustment washers 4G maybe mounted on the rear end 3S of the drive member 39. These washers 4t)are held in place between the rearwardly-facing shoulder of the drivemember 39 and the inside face of the end wall 36 of the handhold 24. Thesplined rear end 33 of the drive member 39 at its extreme end threadedlyreceives a nut 41 that locks the drive member 39 and washers Ait)rigidly in place.

The rear end of the lever 23 is internally threaded, as indicated at 42,for the reception of an adjustment nut 43. This adjustment nut 43 has anovel driving engagement with the drive member 39. The adjustment nut 43is slidably mounted on the forward end of the drive member 39 and isformed with a pair of diametrically opposed transverse bores 44 adaptedto slidably receive outer ends of a drive pin 55. The drive member 39 isformed with a diametrically extending passage 46 in which the drive pin45 is received in a universal joint connection. For this purpose, theopposite radial halves of the passage 46 have a rectangularcross-sectional configuration having an intersection adapted forslidable re ception of the drive pin 45. The passage te has a widthtransversely of the wrench axis adapted to receive pin 45 in a closesliding fit to provide a positive driving connection of the drive member32, pin 45 and adjustment nut 43. However, the opposite sides of eachradial half of the passage 46 that are spaced apart along thelongitudinal axis of the wrench, are tapered to engage the pin i5 at itsmidpoint. inasmuch as the inner diameter of the adjustment nut 43 has aslidable clearance with `the drive member 39, a slight amount ofshifting is permitted between these two members. Accordingly, anymisalignment of these parts can be compensated for by the aforedescribeduniversal joint arrangement inasmuch as the center of the passage i5will tend to center itself on the drive pin 45.

From the foregoing it will be apparent that rotation of the handhold 24will result in axial movement of the drive member 35 in order to alterthe compressive force of the spring 25. However, it is desirable thatrotation of the drive member 3% should not be drivingly transmitted tothe spring 25 inasmuch as the influence of torque on one end of thespring 25 may affect the accuracy of the wrench. In order to avoid anytendency of the spring 25 to rotate along with the drive member 39, adisc 47 is disposed between the rear end of the spring 25 and a smalldiameter crown 43 centrally formed on the forward end of the drivemember 39. Since the crown 43 engages the center of the disc 47 over anarea which is extremely small, there will be little tendency forrotation of the drive member 39 to be transmitted to the spring 25.

As is indicated in FIGURE l, the plunger 26 and hinge 22 are spacedapart a distance X when the wrench is in unbroken condition. Referringto FEGURE 2, it will be seen that when the wrench breaks, the spacingbetween the plunger 25 and hinge 22 will be elongated, due to thecamming action of the cam 27', to a distance Y. As a result, there willbe a change in the internal volume Within the lever 23 forwardly of theplunger 26 and rearwardly of the plunger 26. Accordingly, it isdesirable to provide a means for the free passage of air betweenopposite ends of the plunger 26 in order that the air within the leverwill not be compressed concurrently with breaking of the wrench, suchair compression causing inaccurate results.

In order to avoid such air compression, the plunger 26 preferably ismade from a piece of hexagonal stock material, as indicated in FIGURE 3.The plunger 26 will then contact the interior surface of the lever 23only at spaced-apart points leaving a relatively large volurne ofclearance space between the flat surfaces of plunger 26 and the leverZ3. With this arrangement, the passage of air between opposite sides ofthe plunger is facilitated and no air compression -Will take place. Itshould also be noted that the multi-sided plunger 26 pr-ovides more thanone longitudinally extending line of contact between the plunger andlever '23. Accordingly, the unit stresses imposed on the plunger Z6 whenan input force is applied to the lever 23 are reduced. Frictionalresistance to sliding of the plunger 26 upon breaking of the wrench is`also reduced and the wrench is therefore made more accurate.

In order to provide `lubricant reservoirs for the axially shiftableplunger 26, the plunger is formed with a plurality of reduced-diameterportions 26a adapted to receive a sufficient quantity of lubricant.

A lock ring 9 is provided on the handhold 24 to maintain the compressionof spring 25 at a selected torque limiting force. This lock. ring ismounted on the forward end of the handhold 24 against a forwardly-facingshoulder 50 formed in the handhold and held against this shoulder toprevent relative axial movement by a lock nut 51 that is threadedlyengaged with a reduceddiameter externally threaded forward end portionof the handhold 24.

In order to maintain the wrench at a selected torque limit for which itis set, the lock ring 49 is provided with the mechanism seen in FIGURE6, which is similar'to the locking mechanism disclosed in my Patent No.2,731,855 issued January 24, 1956. Accordingly, this mechanism need notbe described in detail. Suffice it to say that the portion of the lever23 underlying the forward portion of handhold 24 is formed with aplurality of longitudinally extending grooves 52 cor-responding innumber to the Vernier graduations on the forward end of the handhold'24. rihese grooves are adapted to receive one end of a locking butt-on53 that is slidable through -a 'bore 54 formed in the handhold 24 in aportion immediately underlying the lock ring 49.

An arcuate spring 'finger 55 is also connected at one end to thehandhold 2d and at its free end this spring carries the locking button53 for movement into and out of engagement with slots 52 through thebore 5d. In order to accommodate the spring finger 53, the lock ring S9on its inner surface is formed with a spring pocket 56 having an arcuatelength of approximately twice that of the spring finger 55, s-o that thelock ring 49 is capable of limited angular movement relative to thehandhold Z4. At one end the pocket 56 is formed with an enlarged recess57 so that when the parts are in the position shown in FEGURE 6 thelocking button 53 can be moved out of engagement with the groove $2 byrotation of the handhold 2d, the recess 57 permitting sufficient outwardmovement of the locking button 53. When the lock ring i9 is rotated in aclockwise direction from the position in FGURE 6, while the handhold 24is held against rotation, the locking button 53 is prevented from movingradially outwardly of the groove 52 due to the shallowness of the pocket56.

As thus far described, this locking mechanism is substantially the sameas that disclosed in my aforesaid Patent No. 2,731,865. However, thepresent locking mechanism provides a more positive indication of whenthe locking ring is in locked and unlocked position because of thefollowing construction. Thus, it will be noted that the handhold 24 in`a portion immediately underlying an intermediate portion of the springfinger 55 is relieved by a flat surface S8, above which a radiallyoutwardly projecting dimple 59 is formed in the spring finger 5. Thepocket 56 of the lock ring 49 is formed in two steps; a relativelyshallow step 56a in that end of the pocket opposite to the enlargedrecess 57, and a slightly deeper step 56h in that portion of the pocketS6 immediately adjacent the recess 57. A shoulder 6ft is thus formed atthe junction of the steps 56a and Sb. A cavity 61 is formed in theshallow step 56a and is adapted to receive the dimple 59 of the springlinger 5S.

In FIGURE 6 the lock ring 49 is shown in unlocked position so that whenthe handhold 241 is rotated the lock button 53 is cammed out of thegrooves 52 by the sides of the grooves, such displacement of the lockingbutton being permitted by the enlarged recess 57 of the lock ring 49.The distance between the grooves 52 is such that each click which occursupon camming of the lock button out of a groove 52 will indicate adefinite change in foot pounds or inch pounds.

After a desired torque limit has been set into the wrench by rotation ofthe handhold 241, the lock ring 49 is then rotated in a clockwisedirection as viewed in FIGURE 6. When this occurs, the shoulder 60 willfirst ride over the dimple 59 of the spring nger 55 to depress thespring into the relief 58 of the handhold 24. When the cavity 61 is inregistration with the dimple 59, the dimple will engage the cavity andthis resurgence of the spring can be felt on the lock ring 49. At thesame time the fixed end of the spring finger S5 will engage thecounterclockwise end of the pocket 56 and the step 56b will be disposedabove the lock button 53 to reta-in it in the selected groove 52. rl`hewrench is thus securely locked in the desired setting so that whenmanual force is applied to the handhold 24 this input force will notcause any relative rotation between the handhold and the lever 23 andthe desired compression of the spring 25 remains unaffected.

When it is desired to unlock the wrench for adjustment to a new torquelimit, the lock ring 49 is rotated counterclockwise into the positionshown in FIGURE 6. Such rotation of the lock ring first causesdepression of the dimple 59 into the relief 5S due to the camming actionof the walls of the cavity 61. Thereafter, the shailow step 56a ridesover the dimple S9 until the shoulder 6ft has been rotated past thedimple. The dimple 6i) is then permitted to spring outwardly into thedeeper step Sb and the passage of the shoulder 69 over the dimple can befelt on the lock ring 49. This arrangement, therefore, gives a positiveindication that the lock ring 49 is now in completely unlocked positionwith the enlarged recess S7 disposed immediately over the locking button53.

An `alternate form of locking mechanism of greater simplicity is shownin FGURES 9 through 12. ln this forni a tubular handhold 62 is providedwhich is similar' to the handhold 24 but has a reduced-diameter forwardend portion that slidably supports a tubular locking ring 63. As before,the lever 23 is formed with a plurality of longitudinally extendinggrooves 52 in the portion underlying the forward end of the handhold 62and the handhold is formed with a bore 6d adapted to receive a lockingdevice which in this instance takes the for of a ball 65.

The lock ring 63 on its inner surface is formed with an axially disposedslot 66 of varying depth and having a w-idth adapted for the receptionof the locking ball 65. As can be seen in FIGURE 9, the slot 66 at therear end of the lock ring 63 merges into the inner diameter of thelocking ring and increases in depth forwardly to terminate in arearwardly-facing internal shoulder 67. The lock ring 63 is thus heldagainst rotation relative to the handhold 62 but is axially slidablebetween a rearward, unlocked position and a relatively forward, lockedposition.

The locking ball 65 has a diameter greater than the wall thickness ofthe surrounding portion of the hand hold 62. Therefore, when the partsare in the unlocked position of FIGURE 9 rotation of the handheld 62causes the ball 65 to be c-ammed outwardly by the sidewalls of thegroove 52 of the lever 23, the ball 65 being received in the forward endportion of greatest depth of the slot 66. After the handheld 62 has beenset for a desired torque limit of the wrench the lock ring 63 is slidforwardly into the position of FIGURE ll wherein the ball 65 is wedgedbetween a shallower portion of the slot 66 with its inner side against alocking groove S2.

In order to give positive indication of locked and unlocked positions ofthe lock ring 63, the ring on its inner surface is formed with anannular groove 66 that carries a snap ring 69. This snap ring 69 has anormal contracted diameter less than the outer diameter of the handheld62.. The groove 68 has a depth at least as great as the gauge orthickness of the wire material of snap ring 69 so that the snap ring canbe expanded completely into the groove 68 to be carried along with thelock ring 63 over the outer diameter of the handheld 62.

The handheld 62 is formed with a pair of circumferential-ly extendinggrooves 7i) and '71 both of which have a depth less than the radius ofthe wire material of the snap ring 69. The groove 71 is spacedrearwardly of the groove 76 to intersect the ball holding bore 64. Thus,whenever the lock ring 63 is axially shifted along the handhold 62, thesnap ring 69 will contract into engagement with either the groove 7i) or71 to yieldably resist further axial movement of the lock ring, wherebythe lock ring is positioned in locked or unlocked position as the casemay be. In this regard, it will be observed from FIGURE 10 that the snapring 69 has a length less than the circumference of the forward endportion of the handhold 62 so that the ends of the ring do not intrudeinto the slot 66 and will not obstruct relative movement between thelock ring and the handhold.

Referring now to FIGURE 8, there is shown a modified form of a cammember identified generally by the numeral '7 2. The member 72 is alsoof solid cylindrical form and comprises a base 73 formed with anintegral reduceddiameter stem portion 74 extending coaxially from oneend. A plurality of spacer Washers 75 of a thickness and number asdesired are coaxially mounted on the stem 74 against the enlarged headof the base 73 and a relatively thick end spacer 76 than is coaxiallymounted on the stem 74. It will be apparent that all of these parts willbe held in assembled relationship by the force of the spring 25 when themodied cam member 72 is interposed between the rear end of the hinge 22and the front end of the plunger 26. The modified cam member 72 willoperate in precisely the same manner as the solid cylindrical cam 27 butprovides a convenient means of changing the effective length of the camfor the p-urpose of changing the calibration of the wrench from inchpounds into foot pounds.

In operation, the aforedescribed wrench is adjusted to a desired torquelimit by first unlocking the lock ring 49 or 63, as the case may be, androtating the handheld 24 or 62 in the appropriate direction to a desiredtorque limit setting, after which the lock ring is then returned tolocked position. The head 2d is then applied to the load and manualforce applied to turn the lever 23 in either a clockwise orcounterclockwise direction. When the resistance of the load reaches thepreset torque limit, the force of the spring 25 is overcome andcompressed by the camming action of Kthe member 27, which permits slightangular movement of the lever 23 relative to the hinge 22. This breakingof the wrench can be felt when the hinge 22 contacts the wall of thelever 23.

It will be apparent that various modifications and changes may be madewith respect to the wrench construction herinabove described withoutdeparting from G the spirit of the present invention or the scope of thefol-- lowing claims.

I claim:

l. A torque wrench, comprising: a head member formed with aload-engaging means and having a rearwardly extending hinge memberthrough which a torque can be applied to said load-engaging means; alever pivotally connected at its forward end to said hinge member;coacting surfaces on said hinge member and said lever to limit relativeangular movement therebetween; a plunger axially movably mounted in saidlever rearwardly of said hinge member; yieldable means interposedbetween said plunger and said lever to urge said plunger forwardlytowards said hinge member; and a cam means interposed between and havingopposite end flat faces abutting the rear of said 1ninge member and thefront end of said plunger, said cam means, said hinge member and saidplunger being normally held in coaxial alignment with said lever by theforce of said yieldable means, and said yieldable means yielding to anexcessive force applied to said lever to permit relative angularmovement of said hinge member and said lever within the limits of saidcoacting means, said cam means moving out of said coaxial alignment totranslate said excessive force into said relative movement to cause saidyielding, said faces of said cam means having single point contact withsaid hinge member and plunger when said yielding occurs.

2. A torque wrench as set forth in claim 1 in which said cam meanscomprises a cylindrical member interposed between said plunger and saidhinge member and in which the ont end of said plunger and the rear endof said hinge member are each formed with a depression adapted to seatone end of said cylindrical cam in a manner to prevent sliding iof saidend in said depression and also adapted to permit relative angularcamming movement of said cam means, said cam means being normally heldagainst said camming movement by said resilient means.

3. A torque wrench, comprising: a head member formed with load-engagingmeans and having a rear- Wardly extending hinge member through which atorque can be applied to said load-engaging means; a lever pivotallyconnected at its forward end to said hinge member; coacting means onsaid hinge member and said lever to limit relative angular movementbetween said hinge member and said lever; a plunger axially movablymounted in said lever rearwardly of said hinge member; resilient meansinterposed between said plunger and said lever to yieldably urge saidplunger forwardly towards said hinge member; and a cylindrical caminterposed between said plunger and said hinge member, the front end ofsaid plunger and the rear end of said hinge member each being formedwith a depression for seating opposite ends of said cam and adapted tonormally hold said cam in coaxial alignment with said plunger, saidlever and said hinge member under the force of said resilent means, andsaid resilient means yielding to an excessive force applied to saidlever to permit relative angular movement of said hinge member and leverwithin the limits of said coacting means, said cam translating saidexcessive force into said relative movement and into yielding of saidresilient means.

4. A wrench as set forth in claim 3 in which said cam is of a uniformlength and at least one of said depressions comprises a truncated,conical recess having a reduced diameter bottom of a diametersubstantially equal to the diameter of said cam.

5. A wrench as set forth in claim 3 in which said cam is lof uniformlength and at least one of said depressions is a sloping-sided slotparallel to the pivotal axis of said hinge and said lever, and having areduced Width bottom complementary to the diameter of said cam.

6. A torque wrench, comprising: a head member formed with load-engagingmeans and having a hinge member extending rearwardly therefrom through arearwardly facing opening formed in said head member, said opening being`of oblate cylindrical congur-ation ilattened at the pole areas of itsminor axis and said minor axis lying in a plane including the axis ofrotation of said load-engaging means; a tubular lever coaxiallyreceiving said hinge member through the forward end thereof andpivotally connected at its forward end within said plane to said hingemember, the forward end `of said lever being received within saidrearwardly facing opening of said head and having a ldimension in Saidplane adapted for slidable angular movement on said flattened pole areasof said opening, said front end of said lever in the plane of the majoraxis of said oblate opening having a dimension less than said major axisto permit relative angular movement of said lever and said head;coacting means on said hinge member and said lever to limit relativeangular movement therebetween; a plunger axially movably mounted on saidlever rearwardly of said hinge member; resilient means interposedbetween said plunger and said lever to yieldably urge said plungerforwardly towards Said hinge member; and a cam means interposed betweenthe rear of said hinge member and the from end of said plunger, said cammeans, said hinge member and said plunger being normally held in coaxialalignment with said lever by the force of said resilient means and saidresilient means `yielding to an excessive force applied to said lever topermit relative angular movement of said hinge member and said leverwithin the limits of said coaoting means, said cam means translatingsaid excessive force into said relative movement and into yielding ofsaid resilient means.

7. A wrench as set forth in claim 6 in which the pivotal axis of saidlever and said hinge is coaxial with the axis of rotation of saidload-engaging means.

S. A torque wrench, comprising: a head member having a load-engagingmeans and formed with an axially extending passage therethrough ofoblate cylindrical conguration attened at the pole areas of its minoraxis and said minor axis lying in a plane including the axis of rotationof said load-engaging means; a hinge pivotally connected at its forwardend to said head within said passage and extending rearwardly from saidhead, said hinge having a dimension in said plane adapted for slidableangular movement on said iiattened pole areas of said passage and havinga dimension in the plane of the major axis of said passage less thansaid major axis to permit relative angular movement of said hinge andsaid head; a lever pivotally connected at its forward end to said hingemember; coacting means on said hinge member and said lever to limitrelative angular movement therebetween; a plunger axially movablymounted on said lever rearwardly of said hinge member; resilient meansinterposed between said plunger and said lever to yieldably urge saidplunger forwardly towards said hinge member; and a cam means interposedbetween the rear of said hinge member and the front end of said plunger,said cam means, said hinge and said plunger being normally held incoaxial alignment with said lever by the force of said resilient means,and said resilient means yielding to an excessive force applied to saidlever to permit relative angular movement of said hinge and said leverwithin the limits of said coasting means, said earn means translatingsaid excessive force into said relative movement and into said yieldingof said resilient means.

9. A torque wrench, comprising: a head member having a load-engagingmeans and formed with an axially extending counterbored passagetherethrough including an enlarged rearwardly facing opening, saidpassage being of oblate cylindrical configuration flattened at the poleareas of its minor axis and said minor axis lying in a plane includingthe axis of rotation of said load-engaging means; a hinge pivotallyconnected at its forward end to said head in a smaller forward portionof said passage and extending rearwardly therefrom through said enlargedrearward ly facing opening, said hinge having a dimension in said planeadapted for slidable angular movement on said flattened pole areas ofsaid forward portion of said passage and having a dimension in the planeof the major axis of said oblate forward portion of said passage lessthan said major axis to permit relative angular movement of said hingeand said head; a tubular lever coaxially receiving said hinge throughthe forward end thereof and pivotally connected at its forward endwithin said plane to said hinge, the forward end of said leverbeingreceived Within said rearwardly facing opening of said head andhaving a dimension in said plane adapted for slidable angular movementon said flattened pole areas of said opening, said front end of saidlever in the' plane of the major axis of said oblate opening having adimension less than said major axis to permitirelative angular movementof said lever and said head; coacting means on said hinge and said leverto limit relative angular movement therebetween; a plunger axiallymovably mounted on said lever rearwardly of said hinge; resilient meansinterposed between said plunger and said lever to yieldably urge saidplunger forwardly towards said hinge; and a cam means interposed betweenthe rear of said hinge and the front en d of said plunger, said cammeans, said hinge and said plunger being normally held in coaxialalignment with said lever by the force of said resilient means and saidresilient means yielding to an excessive force applied to said lever topermit relative angular movement of said hinge and said lever within thelimits of said coacting means, said cam means translating said excessiveforce into said relative angular movement and into yielding of saidresilient means.

l0. A torque wrench as set forth in claim 9 in which said cam means is acylindrical member of uniform length and in which the front end of saidplunger and the rear end of said hinge are each formed with a depressionadapted to seat one end of said cam means in a manner to prevent slidingof said end in said depression and further adapted to permit relativeangular camming movement of said cam means.

l1. A wrench as set forth in claim l0 in which at least one of saiddepressions comprises a truncated conical recess having a reduceddiameter bottom of a diameter substantially equal to the diameter ofsaid cam means.

l2. A torque wrench as set forth in claim l0 in which at least one ofsaid depressions is a sloping-sided slot parallel to the pivotal axis ofsaid hinge and said lever and having a reduced width bottomcomplementary to the diameter of said cam means.

13. A torque wrench, comprising: a head member with a load-engagingmeans and having a rearwardly extending hlnge member of circularcross-section tapering to a reduced diameter rear end; a cylindricallever adapted to coaxially receive said hinge member into a forward endportion of said lever, said lever having an inner diameter complementaryto the diameter of a transverse circular `section of said tapered hingeand connected to said hinge for pivotal movement about a diametral axis`lying in a plane including the axis of rotation of said load-engagingmeans; ball and socket means formed in the `contacting surfaces of saidhinge member and said lever and having a radius of curvature Whosecenter is coincident with the center of said diametral axis to permitrelative angular movement of said lever and said hinge member, saidtapered hinge member and the interior of said lever providing coactingmeans to limit said relative angular movement; a plunger axially movablymounted on said lever rearwardly of said hinge member; resilient meansinterposed between said plunger and said lever to yieldably urge `saidplunger forwardly towards said hinge member; and a cam means interposedbetween the rear of s aid hinge member and the front end of saidplunger, said cam means, said hinge and said plunger being normally heldin coaxial alignment with said lever by the force of said resilientmeans and said resilient means yielding to an excessive force applied tosaid lever to permit relative angular movement of s aid hinge member andsaid lever within the limits of said coacting means, said cam meansvtranslating said excessive force into said relative movement and intoyielding of said resilient means.

14. A torque wrench, comprising: a head member having a load-engagingmeans formed with an axially extending counterbored passage of oblatecylindrical configuration including an enlarged rearwardly facingopening,

said passage being flattened at the pole areas of its minor axis andsaid minor axis lying in a plane including the axis of rotation of saidload-engaging means; a hinge pivotally connected at its forward end tosaid head in smaller forward portion of said oblate passage andextending rearwardly therefrom through said enlarged rearwardly facingopening, said hinge having a dimension in said plane adapted forslidable angular movement on said flattened pole areas of said forwardportion of said passage and having a dimension in the plane of the majoraxis of said oblate forward portion of said passage less than said majoraxis to permit relative angular movement of said hinge and said head; atubular lever coaxially receiving said hinge member through the forwardend thereof and pivotally connected at its forward end within said planeto said hinge member, the forward end of said lever being receivedwithin said rearwardly facing opening of said head and having adimension in said plane adapted for slidable angular movement on saidflattened pole areas of said opening, said front end of said lever inthe plane of the major axis of said oblate opening having a dimensionless than said major axis to permit relative angular movement of saidlever and said head, said hinge being of circular cross-section taperingto a reduced diameter rear end and said lever having an inner diametercomplementary to the diameter of a transverse circular section of saidtapered hinge and connected to said hinge for pivotal movement about adiametral axis lying in said plane; ball and socket means formed in thecontacting surfaces of said hinge and said lever and having a radius ofcurvature whose center is coincident with the center of said diametralaxis to permit relative angular movement of said lever and said hinge,said tapered hinge and the interior of said lever providing coactingmeans to limit said relative angular movement; a plunger axially movablymounted on said lever rearwardly of said hinge member; resilient meansinterposed between said plunger and said lever to yieldably urge saidplunger forwardly towards said hinge; and a cam means interposed betweenthe rear end of said hinge and the front end of said plunger, said cammeans, said hinge and said plunger being normally held in coaxialalignment with said lever by the force of said resilient means and saidresilient means yielding to an excessive force applied to said lever topermit relative angular movement of said hinge and said lever within thelimits of said coacting means, said cam means translating said excessiveforce into said relative angular movement and into yielding of saidresilient means.

15. A torque wrench as set forth in claim 14 in which said cam meanscomprises a cylindrical member of uniform length and in which the frontend of said plunger and the rear end of said hinge are each formed witha depression adapted to seat one end of said cylindrical cam, each ofsaid depressions being formed with sloping sides tapering to a bottomoor of a reduced width complementary tothe diameter of said cam meansand adapted to prevent sliding of said cam means and to permit relativeangular camming movement of said cam means.

16. A torque wrench as set forth in claim 14 in which the pivotal axisof said lever and said hinge is coaxially disposed with the axis ofrotation of said load-engaging member.

17. A torque wrench, comprising: a head member formed with load-engagingmeans and having a rearwardly extending hinge member through which atorque can be applied to said load-engaging means; a tubular leveradapted to coaxially receive said hinge member Ythrough the front end ofsaid lever and pivotally connected at said front end to said hingemember; coacting means on said hinge member and lever to limit relativeangular movement therebetween; a plunger axially slidably mounted insaid lever rearwardly of said hinge member and having a cross-sectionalconfiguration dissimilar to the cross-sectional configuration of theinterior of said lever to provide air passage clearance space betweensaid plunger and said lever; resilient means interposed between saidplunger and said lever to yieldably urges said plunger forwardly towardsaid hinge member; and a cam means interposed between the rear of saidhinge member and the front end of said plunger, said cam means, saidhinge member and said plunger being normally held in coaxial alignmentwith said lever by the force of said resilient means and said resilientmeans yielding to an excessive force applied to said lever to permitrelative angular movement of said hinge member and said lever within thelimits of said coacting means, said cam means translating said excessiveforce into said relative angular movement and into yielding of saidresilient means.

18. A torque wrench as set forth in claim 17 in which said lever is ofcylindrical configuration and said plunger is of polygonalconfiguration.

19. A torque wrench, comprising: a head member formed with load-engagingmeans and having a rearwardly extending hinge member; a tubular levercoaxially receiving said hinge member through the forward end of saidlever and pivotally connected at its forward end to said hinge member;coacting means on said hinge member and said lever to limit relativeangular movement therebetween; a plunger axially movably mounted withinsaid lever rearwardly of said hinge member; spring means within saidlever rearwardly of said plunger and interposed between said plunger andsaid lever to yieldably urge said plunger forwardly towards said hingemember; a cam means interposed between the rear end of said hinge memberand the front end of said plunger, said cam means, said hinge member andsaid plunger being' normally held in coaxial alignment with said leverby the force of said spring means and adapted to translate an excessiveforce applied to said lever into relative an gular movement of saidlever and hinge member and into yielding of said spring means; a tubularhandheld telescopically mounted on the rear end of said lever; a drivemember coaxially mounted within the rear end of said lever to abut therear end of said spring means and rotatably drivingly engaged by saidhandheld; an adjustment nut threadedly engaged with the interior of saidlever for axial adjustment along said lever and adapted to coaxiallyreceive the forward end of said drive member; and means rotatablydrivingly interconnecting said adjustment nut and said drive member andhaving a universal joint connection with said drive member wherebyrotation of said handhold axially moves said nut and drive member tovary the force exerted by said spring, said universal joint connectionserving to retain said drive member in axial alignment with said lever.

20. A wrench as set forth in claim 19 in which a disc is interposedbetween the rear end of said spring means and the front end of saiddrive member and said drive member is formed on its front end with asmall central crown rotatably abutting the center of said disc, wherebyactuation of said adjustment means is prevented from rotating saidspring means by rotation of said crown on said disc.

21. In a torque wrench having spring means and means to adjust the forceof said spring means, a locking mechanism for said adjustment meansincluding: a cylindrical lever; a cylindrical handhold telescopicallymounted on said lever; a drive means threadedly engage with said leverand drivingly engaged by said handheld and adapted to vary the force ofsaid spring means in response to rotation of said handhold; a lockingball carried by a bore formed in the wall of said handhold and having adiameter greater than the wall thickness of said handhold; and a lockmember mounted on said handhold for movement over said ball betweenlocked and unlocked positions thereof, said lock member on its innerface having a cam surface that forces said ball to rotrude inwardiybeyond said handhold when said lock member is in locked position,whereby said ball is wedgingly seated by said lock member in one of aplurality of longitudinally extending grooves formed in said lever, saidcam surface when said lock member is in unlocked position permittingsaid lock ball to be cammed out of said groove by the walls of saidgrooves.

22. A locking mechanism as set forth in claim 2l in which said lockmember comprises a sleevelike ring axially slidably mounted on saidhandhold and said cam surface is defined by the bottom of alongitudinally disposed slot formed in the inner surface of said ring.

23. A locking mechanism as set forth in claim 22 in which said ring isformed with an internal annular groove intersecting said slot and a snapring of lesser thickness than the depth of said slot is carried in saidslot, and said handheld is formed with a pair of circumferentiallyextending grooves of lesser depth than one half the thickness of saidsnap ring and into which said snap ring is selectively releasablyreceivable by movement of said lock ring to said locked and unlockedpositions corresponding with engagement of said snap ring with one orthe other of said grooves.

24. In a torque wrench having spring means and means to adjust the forceof said spring means, a locking mechanism for said adjustment meansincluding: a cylindrical lever; a cylindrical handhold telescopicallymounted on said lever; a drive means threadedly engaged with said leverand drivingly engaged by said handhold and adapted to vary the force ofsaid spring means in response to rotation of said handhold; a lockingbutton radially movable through a bore formed in the wall of saidhandhold, said button when inwardly depressed engaging one of aplurality of longitudinally extending grooves formed in said lever toprevent relative rotation of said lever and said handhold; a springfinger having one of its ends retained by said handhold and adapted tocarry said button at its other end and formed with an outwardly pointingdimple intermediate the ends of said finger; and a lock ring journaledon said handhold over said spring finger and formed on its inner facewith a pocket of greater circumferential length than said finger and inwhich said finger is enclosed, said pocket at one end having an enlargedrecess within which said button is outwardly movable out of engagementwith said grooves of said lever when Said ring is in an unlockedposition, said pocket intermediate its ends having a shoulder foroverriding said dimple of said finger and also having a cavity adaptedto register with and receive said dimple when said ring is in a lockedposition to yieldably retain said ring in said locked position, saidpocket having a depth to prevent movement of said button out of saidgrooves of said lever when said ring is in a position other thanunlocked, said handheld under said finger being relieved to permitdepression of said finger in response to said overriding engagement ofsaid shoulder and said dimple.

25. In a torque wrench the combination, comprising: a head member havinga load-engaging means; a hinge member hingedly connected to said headmember and extending rearwardly from said head member, said membershaving coacting means to limit relative angular movement therebetween; alever pivotally connected at its forward end to said hinge member, saidlever and hinge member having coasting means to limit relative angularmovement therebetween; a plunger axially movably mounted in said leverrearwardly of said hinge member and yieldably biased toward said hingemember; and a torque-limiting means between adjacent ends of said hingemember and said plunger for depressing said plunger when an excessivetorque is applied to said load-engaging means.

26. ln a torque wrench the combination comprising: a head member havinga load-engaging means; a hinge member hingedly connected to said headmember on a hinge axis parallel to the axis of said load-engaging means,said hinge member extending rearwardly from said head member, saidmembers having coacting means to limit relative angular movementtherebetween; a lever pivotally connected at its forward end to saidhinge member on a pivot axis in alignment with the axis of saidload-engaging means, said lever and hinge member having coacting meansto limit relative angular movement therebetween; a plunger axiallymovably mounted in said lever rearwardly of said hinge member andyieldably biased towards said hinge member; and a torque-limiting meansbetween adjacent ends of said hinge member and plunger for depressingsaid plunger when an excessive torque is applied to said load-engagingmeans.

27. ln a torque wrench the combination comprising: a head member formedwith a passage therethrough and having a load-engaging means whose axisis normal to the axis of said passage; a hinge member having its forwardend receivable in said passage and hingedly connected to said headmember on a hinge axis parallel to the axis of said load-engagingmember, said hinge axis being spaced forwardly from the axis of saidloadengaging member, said hinge member extending rearwardly from saidhead member, said members having coacting surfaces to limit relativeangular movement therebetween; a tubular lever within whose forward endthe rearwardly extending portion of said hinge member is received, saidlever being pivotally connected at its forward end to said hinge memberon a pivot axis in alignment with the axis of said load-engaging member,said lever and said hinge member having coacting means to limit relativeangular movement therebetween; a plunger axially movably mounted withinthe rear end of said lever rearwardly of said hinge member and yieldablybiased towards said hinge member; and a torque-limiting cam meansinterposed between and having opposite ends faces abutting the rear ofsaid hinge member and the front end of said plunger, said cam means,said hinge member and said plunger being normally held in coaxial align*ment with said lever by said yieldably biased plunger.

28. In a torque wrench the combination comprising: a head member formedwith a load-engaging means and having a rearwardly extending hingemember through which a torque can be applied to said load-engagingmeans; a tubular lever within whose front end the rearwardly extendingportion of said hinge member is receivable, said lever being pivotallyconnected at its forward end to said hinge member, said lever and hingemember having Contact only through a ball and socket means defined onthe interior surface of said lever and exterior surface of said hingemember in the region of the pivot axis of said hinge member and lever;coacting means on said hinge member and said lever to limit relativeangular movement therebetween; a plunger axially movably mounted in saidlever rearwardly of said hinge member; yieldable means in said lever tourge said plunger forwardly toward said hinge member; and a cam meansinterposed between the rear of said hinge member and the front end ofsaid plunger, said cam means, said hinge :member and said plunger beingnormally held in coaxial alignment with said lever by the force of saidyieldable means, said yieldable means yielding to an excessive forceapplied to said lever to permit relative angular movement of said hingemember and said lever within the limits of said coacting means, said cammeans translating said excessive force into said relative movement tocause said yielding.

(References on following page) References Cited in the le of this patent2,732,747 Livermont an. 31, 1956 2,743,638 Woods May 1, 1956 UNITEDSTATES PATENTS 2,789,454 Woods Apr. 23, 1957 2,686,446 Livermont Aug.17, 1954 2,792,733 Walraven et a1. May 21, 1957 2,704,472 Booth Mar. 22,1955 5 2,887,919 Aijala May 26, 1959 2,731,865 Woods Jau 24, 19562,837,921 Livermont May 26, 1959

